Process for the hydrogenation of water-miscible acetylene compounds into olefin compounds



United States Patent 3,450,776 PROCESS FOR THE HYDROGENATION OFWATER-MISCIBLE A CETYLEN E C OM- POUNDS INTO OLEFIN COMPOUNDS AlessandroDi Cio and Marcello Massi Mauri, Milan, Italy, assignors to SnamProgetti S.p.A., Milan, Italy, a. corporation of Italy N 0 Drawing.Continuation-impart of application Ser. No. 364,759, May 4, 1964. Thisapplication Feb. 16, 1968, Ser. No. 705,930

Int. Cl. C07c 29/00, 31/12, 31/18 US. Cl. 260-635 4 Claims ABSTRACT OFTHE DISCLOSURE The present invention relates to a process for theselective hydrogenation of water-miscible acetylene compounds. Thisapplication is a continuation-in-part of our pending application, Ser.No. 364,759, filed May 4, 1964, and now abandoned.

It is already known that it is possible selectively to hydrogenateacetylene compounds to form olefin compounds in the presence ofpalladium-based catalysts. In prior cases, however, there has alwaysbeen production of at least 2%3% of saturated compounds. Selectivity, asa matter of fact, never exceeds, by operating this way, 97%98%. In orderthat higher selectivity ratings may be achieved, it has been suggestedpartially to deactivate the palladium catalyst by impregnation orco-precipitation with salts of Pb, Zn, Hg, Cd, Th, Sn and others.

In the known processes, however, it is necessary first to prepare thecatalyst by treating the catalyst wtih the zinc or other poisoning salt.Only then could such a hydrogenation process be carried out.

These known impregnation or co-precipitation methods, moreover, can beperformed, in practice, only with difficulty, in that the de-activationconditions of the catalyst (temperature, concentration of thede-activating salt, duration of the operation) are extremely critical;and it is difficult to obtain uniformity in preparation of the poisonedcatalyst.

It is likewise known that, in order that a highly selective catalyst maybe produced, it is necessary that the impregnation or de-activation stepbe carried out at somewhat high temperatures (from 80 C. to 100 C.) andthis, inter alia, is an unfavorable circumstance, particularly ifsupported catalysts are concerned.

Such difliculties are particularly serious when the hydrogenationprocess is to be continuous.

We have discovered that, in the hydrogenation of watermisci-bleacetylene compounds through the use of a palladium-based catalyst, it ispossible to condition the catalyst, which may be furnished with aconventional supporting mass such as calcium carbonate or bariumsulfate, to attain a 100% selectivity even in the cold or at least attemperatures in the range 20 C.-60 C. and to maintain the catalyst incondition to attain that selectivity over an extended period, by feedingthereto a reaction mixture which includes, in aqueous solution, 0.01% to3,450,776 Patented June 17, 1969 ice 5.0%, based on the weight of theacetylene compound, of a zinc salt. In the practice of our invention thesalt employed is a member of the group consisting of zinc acetate, zincsulfate, zinc nitrate, zinc chloride and zinc oxalate; and hydrogenationoccurs at a pressure between 1 and 20 atmospheres, preferably in thepresence of about 0.5% (by weight of the acetylene compound) of an aminecompound. Through the practice of our invention, the difiicultiesinherent in prior methods, which have been referred to above, areavoided and good uniformity in the poisoning of the catalyst is insured.

By operating according to the present invention it is not at allnecessary, in order to have selectivity, to subject the palladiumcatalyst to impregnation in hot condition or to co-precipitation stepswhich are burdensome and complicated, since the zinc is continuallyadded, in the form of a soluble compound, with the hydro genationmixture.

In addition to this paramount operational and economical advantage, thepresent invention represents a further advancement in that the lifetimeof the catalysts employed according to the invention is longer than thatof the conventional de-activated catalysts, the respective selectivitiesbeing equal.

According to our invention, it is possible to cause the material to behydrogenated and the zinc salt to pass over the catalyst several tens oftimes during continuous test runs, obtaining in any case a maximumselectivity rating.

The anion moiety of the zinc salt is immaterial to the ends ofselectivity, it being preferable, however, that the salt itself be atleast fairly water-soluble. Chlorides, sulfates, nitrates, acetates andoxalates lend themselves very well to this purpose.

The amount of salt may be varied between 0.01% and 5% and preferablyfrom 0.01% to 2% on a weight basis with respect to the acetylenecompound.

The invention can also be applied to diluted aqueous solutions of theacetylene compound, in that the presence of large amounts of water doesnot impair in the slightest the reaction selectivity.

It is preferable to add to the reaction mixture an amine compound,generally ammonia, in very slight amounts, preferably less than 0.5 ona. weight basis with respect to the acetylene compound. Larger amounts,up to 20%- '30%, do not produce, however, any detrimental effect uponthe reaction. The salient feature of the present invention, however, isnot the use of amines, nor is it the composition of the hydrogenationcatalyst. It is, rather, the carrying out of the hydogenationsimultaneously with the poiosning, and, if desired, in a continuousmanner by feeding onto the catalyst, not in itself selective, both thesolution of the compound to be hydrogenated and the solution of the zincor other poisoning salt.

The present invention can be applied both to continuous or batchprocesses within a wide temperature range e.g. between 20 C. and 60 C.and within a Wide pressure range eg from 1 to 20 atmospheres.

It should be noted that the amount of salt to be added to the reactionmixture is a function, within the above indicated limits, of thereaction velocity, i.e. of the hydrogen pressure and temperature, aswill be explained more in detail in the examples to follow.

By operating according to the present invention, the absorption ofhydrogen by the reacting mixture ceases once the triple bond ishydrogenated in a double bond, after which, even though the reactedmixture be allowed to stay in the reaction mixture even for a relativelylong time, no further hydrogenation takes place.

The present disclosure will be better illustrated by the followingoperative examples.

3 EXAMPLE 1 By hydrogenating 2-methyl-3-butyn-2-ol in the form of anazeotropic mixture with water (26% water by weight), in the presence of1% by weight of a catalyst consisting of palladium on a calciumcarbonate support Pd) and of 0.1% by weight of ammonia with respect tothe methylbutynol, in an autoclave with stirring and under theabove-described temperature and pressure conditions, 100% selectivityhas always been attained, along with the stoppage of the reaction afterthe absorption of the hydrogen amount theoretically corresponding to thequantity which is necessary for the hydrogenation of the triple bondonly, by adding the weight percentages of Zinc acetate indicated in thetable below.

Temperature, Pressure Percent Zn C. atmospheres acetate EXAMPLE 22-methyl-3-butyn-2-ol has been hydrogenated, in the form of anazeotropic mixture with water, at 1 atmosphere and at 50 C. with severalsalts, as specified in the table below, always obtaining 100%selectivity.

In order to test the catalyst lifetime, an autoclave fitted with astirrer has been charged with 100 grs. of an azeotropic mixture of2-methyl-3-butyn-2-ol and water, 1 gram of Pd (CaCO -supported, 5% Pd),0.1 gram zinc acetate and 0.1 gram ammonia: hydrogen has been allowed tobe absorbed at 1 atmosphere and 60 C. temperature until the reaction wasover. The liquid fraction has been removed by decantation and, on thecatalyst left on the bottom of the autoclave, there have been introduced100 grs. of an azeotropic mixture of methylbutynol and water, 0.02 gr.zinc acetate and 0.1 gr. ammonia, causing hydrogen to be absorbed. Thisoperational sequence has been repeated 50 times. The reaction stopsafter absorption of the hydrogen amount necessary according to theoryfor the formation of methylbutenol. A selectivity of virtually 100% isachieved and the same reaction velocity throughout all the tests, hasbeen ascertained.

EXAMPLE 4 An autoclave equipped with stirrer, kept at 1 atmosphere andC., has been charged with 500 grs. 2-butyn- 1,4-diol, 20 grs. water, 0.5gr. Zn(COOCH 5 grs. Pd/

CaCO (5 Pd) and 0.1 gr. NH Once the theoretical amount of hydrogen hasbeen absorbed, the reaction has ceased and a quantitative yield of2-buten-1,4-dio1 has been obtained.

EXAMPLE 5 A tubular reactor, thermostatically kept at C., is continuallyfed in uniflow conditions, with 30 liters an hour of an azeotropicmixture of methylbutynol and water containing 1% of Pd/CaCO (5% Pd),0.2%

0.02% NH and 5 normal cubic meters of hydrogen. By working at a pressureof 6 atmospheres a product is obtained which contains no saturatedcompounds but only a slight trace of acetylenic alcohol.

What is claimed is:

1. A process for the selective hydrogenation of an acetylenic compoundselected from the group consisting of 2-methyl-3-butyn-2-ol and2-butyn-1,4-diol into the corresponding olefin compound which comprisesfeeding the acetylene compound, mixed with water and an aqueous solutionof a zinc salt selected from the group consisting of zinc acetate, zincsulfate, zinc nitrate, zinc chloride and zinc oxalate, onto apalladium-based catalyst, the selective hydrogenation being effected ata temperature between 20 C. and C. and at a pressure between 1 and 20atmospheres, the weight of the zinc salt being between 0.01% and 5% ofthe weight of the acetylene compound.

2. The process according to claim 1 wherein the Weight of the zinc saltis between 0.01% and 2% of the weight of the acetylene compound.

3. The process according to claim 1 wherein the reaction is carried outin the presence of an amine compound.

4. The process according to claim 3 wherein the amine compound isammonia in an amount about 0.5% by weight of the acetylene compound.

References Cited UNITED STATES PATENTS 2,207,070 7/1940 Reppe et al.2,267,749 12/1941 Reppe et al. 2,335,795 11/1943 Reppe et al. 2,516,8267/ 1950 Smith.

FOREIGN PATENTS 1,190,949 4/1959 France.

658,801 3/1963 Canada.

LEON ZITVER, Primary Examiner.

J. E. EVANS, Assistant Examiner.

US. Cl. X.R. 252-473; 260-642

